This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
| n | a(n) |
|---|---|
| 2 | 1 |
| 3 | 0 |
| 4 | 4 |
| 5 | 5 |
| 6 | 58 |
| 7 | 217 |
| 8 | 2035 |
| 9 | 13470 |
| 10 | 134164 |
| 11 | 1243770 |
| 12 | 14129410 |
| 13 | 164244808 |
| 14 | 2151576620 |
| 15 | 29671566836 |
| 16 | 444758323628 |
| 17 | 7055358559376 |
| 18 | 119546765395744 |
| 19 | 2139179551573104 |
| 20 | 40486788832168944 |
| 21 | 805969129348431936 |
| 22 | 16860672502118423136 |
| 23 | 369459637224850523808 |
| 24 | 8467140450141232328160 |